Heat butter in saucepan over medium heat. Sprinkle in flour while whisking vigorously. Cook for a minimum of 5 minutes while stirring/whisking constantly. Roux may be cooked for up to 20 minutes until it just begins to turn blonde. In a hot stock pan, cook diced onion, garlic and jalapeno in oil for 2 minutes. Add crab stock and crab meat and cook for an additional 3–5 minutes. Add tomatoes and cream, stir thoroughly and bring to a boil. Thicken to desired constituency with roux.